Battlecruiser, or battle cruiser, was a formal designation for the class of massive ships that fell between Star Destroyers and Dreadnaughts in size.[1]
In informal use, it was used for the largest and strongest warships in a fleet that were not battleships, as well as more generally for various types of warships, along with "cruiser".[2]

Often nicknamed a "Heavy Star Destroyer," it was a 2,200m vessel that saw service throughout the Empire, and was also utilized within the reborn Emperor's empire. It also acted as a good example of the cruiser subclass of battlecruiser.

The Praetor Mark II-class was an Imperial battlecruiser designed and unveiled during the early stages of the Galactic Empire's formation. Few were made largely due to the costs, lack of versatility, and lack of a terror-inducing shape of the Star Destroyers and the Star Dreadnoughts, respectively.

This line of battlecruisers, which possessed a similar design to the Star Destroyer-class, belonged to the House of Tagge and was pledged to aid the Imperial warships blockading the Gordian Reach after the Battle of Yavin in 0 ABY. The presence of the Tagge warships and their commander, GeneralUlric Tagge, allowed family patriarch Orman Tagge to conduct private operations under the Empire's radar.

In Naval terms, battlecruisers are a type of naval warship that acted as an intermediary between battleships and cruisers. Namely, possessing a battleships armament while retaining a cruisers thickness of armour. They were prevalent during the first half of the 20th century, although by the end of World War II and the beginning of the Cold War, they fell into disuse.

According to Jason Fry's Endnotes for The Essential Guide to Warfare, the battlecruisers were "neither fish nor fowl", although he had fun going back to Giel's previously unnamed flagship, the Helmsman.